1. Field of the Invention
The present invention relates to apparatus for material handling and, in particular, to apparatus for grasping for lifting a roll of material having its eye disposed in a horizontal orientation.
2. Description of the Prior Art
In a myriad of industrial settings, a troublesome material handling problem relates to the manipulation of a roll of a given material. Frequently, such rolls comprise a metallic material such as steel or aluminum, but they may also consist of other materials including plastics, textiles or paper products. Such rolls of material are formed with an eye which may be oriented vertically or horizontally.
While the prior art includes means for lifting rolls having a vertical eye, such means typically simply grasp the outer diameter of the roll prior to lifting. As is well known in the industries involved, and especially those involving rolls of metallic materials, such grasping virtually always disfigures the outer wraps of material as well as deforming the cylindrical shape of the material. Obviously, in relation to the former condition, the disfigured material must be scrapped. However, regarding the deformation of the roll, the apparatus for working on the rolled material usually operates at high speeds, which operation will be readily seen to be especially dangerous if the roll is out of round.
As such, it has proven expedient to handle rolls of material, which material will, by means of example only, be herein referred to as a web of metallic material, with the eye oriented horizontally. Typical prior art apparatus for handling a horizontal roll includes a tong suspended from a remotely operated overhead crane. The tong usually includes a central body portion including a gear system for horizontally displacing a pair of vertical lifting legs. Such legs are provided with lifting portions which are caused to surround the roll and enter the inside diameter of the roll when the legs are brought together. The lifting surface is then raised to engage the roll's eye prior to roll lifting.
While such tongs avoid some of the drawbacks of the vertical eye lifting apparatus, prior art tongs are beset with a host of difficulties of their own. Frequently, such tongs are employed in an environment which includes a multiplicity of rolls in close proximity to one another. When the crane operator brings the tong's legs adjacent the roll to be lifted, due to the usually considerable distance between the operator and the tong, the tong legs are often caused to strike the roll to be lifted as well as adjacent rolls thereby damaging various portions thereof and especially the edges. Further, when the lifting surfaces of the tong legs are disposed at an elevation within the inner diameter of the roll and the legs are brought together or closed, the remote operator has no clear way of ascertaining when the inner surfaces of the legs engage the ends of the roll. As such, the operator usually runs the legs inward until they strike the roll ends thereby damaging the roll ends and the lifting legs as well as severely jarring the tong's gear box.
Next, during a typical lift, the tong is raised until the lifting surface engages the roll's inner diameter. It will be readily appreciated that during the lifting of the tong relative to the roll while the inner surfaces of the lifting legs engage the roll ends, the lifting legs are caused to scrape against, and, hence, severely damage such roll ends. Obviously, all of the above-discussed situations result in the scrapping of an extreme amount of costly semi-finished product costing industry untold dollars annually.
The prior art has attempted to deal with the problem of scraping the lifting legs against the roll ends by providing a sliding device on the inner surface of the lifting legs. In such a device, the legs engage the roll and the sliding device slides with the roll relative to the lifting leg. A counterweight and pulley system may be provided to return the sliding member to its original position following the lift.
It is clear that such prior art apparatus is, however, replete with most of the problems of the other prior art apparatuses. For example, no means is known for protecting the roll and adjacent rolls from damage during tong positioning. Also, and very importantly, there is no known means for protecting the roll or the tong from harm during the closing of the legs about the roll.
The subject invention is directed toward an improved apparatus for grasping for lifting a roll of material which overcomes, among others, the above-discussed problems and which is effective to grasp a horizontal roll without damaging the roll in question, adjoining rolls or the apparatus itself.